The amount of direct sunlight which a proposed structure will receive in a year, as well as the times of day, of the exposures have long been considered an important consideration for the designers of structures. Depending upon the climate where the building is to be situated, designer may locate windows and doors on the sun or shade side of the structure corresponding to whether or not the sun can be advantageously employed as a supplemental source of light and heat.
A critical need for advance knowledge of sunlight exposure has arisen with the increased utilization of solar energy as a source of heating, cooling, or power generation. This advance knowledge is essential if solar power is to be a viable and economically feasible energy alternative in any given application.
Where the use of solar energy is being considered, it is essential to know the aggregate sunlight exposure at the location of utilization. The exposure calculations, when combined with existing solar data and calculations of the angles of solar radiation, taken together with such variables as probable cloud cover, enables an accurate determination of the available solar power in advance of costly implementation.
Numerous prior art devices for measuring the degree of exposure of a preselected reference point to direct, natural sunlight are known in the art, for example, the device of Sylvester disclosed in U.S. Pat. No. 2,884,697 issued in 1959. Devices of such type require scale models of structures and other natural obstructions to direct sunlight which can be placed in juxtaposition within a hemisphere into which movable light, representing the sun, is directed tracing the normal path of the sun relative to the models. Such devices provide a simulation of direct sunlight exposure, but suffer the disadvantages of requiring the preparation of scale models and do not facilitate the production of a graphical representation of aggregate sunlight exposure.